This invention relates to medico-surgical instruments.
The invention is more particularly concerned with instruments for use in epidural and spinal anaesthesia.
Spinal anaesthesia relies on the administration of small quantities of an anaesthetic agent into the dura, or subarachnoid. This is a relatively simple procedure and has the further advantages of being quick-acting and producing good muscle relaxation. The disadvantages, however, of this procedure are that it is only effective for short periods and that penetration of the dura can produce a severe headache in the patient.
It is common practice now to use spinal anaesthesia in conjunction with epidural anaesthesia which, though being slower to act, and less effective at muscle relaxation, has the advantage of being easier to prolong anaesthesia by the repeated or continual administration of an anaesthetic agent via an epidural catheter. Thus, a spinal anaesthetic is administered initially which is followed by continual epidural anaesthesia for the desired period.
Usually, the spinal and epidural insertions are made at separate sites but it has been found to be advantageous to carry out both procedures at the same site since this reduces discomfort of the patient and shortens the time taken to administer the anaesthetic. It has been proposed to use a Tuohy needle to locate the epidural space in the usual way, and then to insert a spinal needle through the Tuohy needle so that it emerges from the tip of the Tuohy needle and penetrates the dura. An anaesthetic agent can then be administered through the spinal needle. The spinal needle is subsequently withdrawn, leaving the Tuohy needle in position for use in introduction of an epidural catheter in the usual way.
During epidural and spinal anaesthesia, in order to reduce discomfort of the patient, it is important that the sharp, inclined tips of both the Tuohy and spinal needles are aligned with the "grain" of the tissues through which they are inserted so that cutting of the tissue is minimized and healing facilitated.